In the well-known process of electrostatographic or xerographic printing, an electrostatic latent image is formed on a charge-retentive imaging surface, and then developed with an application of toner particles. The toner particles adhere electrostatically to the suitably-charged portions of the imaging surface. The toner particles are then transferred, by the application of electric charge, to a print sheet, forming the desired image on the print sheet. An electric charge can also be used to separate or “detack” the print sheet from the imaging surface.
For the initial charging, transfer, or detack of an imaging surface, the most typical device for applying a predetermined charge to the imaging surface is a “corotron,” of which there are any number of variants, such as the scorotron or dicorotron. Common to most types of corotron is a bare conductor, in proximity to the imaging surface, which is electrically biased and thereby supplies ions for charging the imaging surface. The conductor typically comprises one or more wires (often called a “corona wire”) and/or a metal bar forming saw-teeth, the conductor extending parallel to the imaging surface and along a direction perpendicular to a direction of motion of the imaging surface. Other structures, such as a screen, conductive shield and/or nonconductive housing, are typically present in a charging device, and some of these may be electrically biased as well. The corotron will have different design parameters depending on whether it is being used for initial charging, transfer, or detack.
In a practical application of charging devices, dust and other debris may collect in or around the corotron. Clearly, the presence of such material will adversely affect the performance of the corotron, and may cause dangerous arcing conditions. Therefore periodic cleaning of the charging device is often desired, and many schemes exist in the prior art for cleaning the charging device, such as by wiping the bare conductor. In high-end printing machines, this wiping may be performed by a motorized wiper which travels along the corotron wire; this wiper may be moved by a pulley or lead screw.
The present disclosure relates to a mechanism, and control system therefor, which wipes a corotron wire or similar structure in a printing apparatus.